Precisely Tailoring Upconversion Dynamics Via Energy Migration in Core-Shell Nanostructures

UvA-DARE (Digital Academic Repository)

Precisely Tailoring Upconversion Dynamics via Energy Migration in Core-Shell Nanostructures

Zuo, J.; Sun, D.; Tu, L.; Wu, Y.; Cao, Y.; Xue, B.; Zhang, Y.; Chang, Y.; Liu, X.; Kong, X.; Buma, W.J.; Meijer, E.J.; Zhang, H. DOI 10.1002/anie.201711606 10.1002/ange.201711606 Publication date 2018 Document Version Final published version Published in Angewandte Chemie, International Edition License CC BY-NC Link to publication

Citation for published version (APA): Zuo, J., Sun, D., Tu, L., Wu, Y., Cao, Y., Xue, B., Zhang, Y., Chang, Y., Liu, X., Kong, X., Buma, W. J., Meijer, E. J., & Zhang, H. (2018). Precisely Tailoring Upconversion Dynamics via Energy Migration in Core-Shell Nanostructures. Angewandte Chemie, International Edition, 57(12), 3054-3058. https://doi.org/10.1002/anie.201711606, https://doi.org/10.1002/ange.201711606

General rights It is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), other than for strictly personal, individual use, unless the work is under an open content license (like Creative Commons).

Disclaimer/Complaints regulations If you believe that digital publication of certain material infringes any of your rights or (privacy) interests, please let the Library know, stating your reasons. In case of a legitimate complaint, the Library will make the material inaccessible and/or remove it from the website. Please Ask the Library: https://uba.uva.nl/en/contact, or a letter to: Library of the University of Amsterdam, Secretariat, Singel 425, 1012 WP Amsterdam, The Netherlands. You willUvA-DARE be contacted is a service as provided soon as by possible.the library of the University of Amsterdam (https://dare.uva.nl)

Download date:26 Sep 2021 Angewandte Communications Chemie

International Edition:DOI:10.1002/anie.201711606 Upconversion German Edition:DOI:10.1002/ange.201711606 Precisely Tailoring Upconversion Dynamicsvia Energy Migration in Core–Shell Nanostructures Jing Zuo+,Dapeng Sun+,Langping Tu+,Yanni Wu,Yinghui Cao,Bin Xue,Youlin Zhang, Yulei Chang,Xiaomin Liu, Xianggui Kong,* Wybren JanBuma, Evert JanMeijer,* and Hong Zhang* Abstract: Upconversion emission dynamics have long been biology,[2] anti-counterfeiting,[3] and solar cells.[4] Recent believed to be determined by the activator and its interaction advances in upconversion emission applications rely more with neighboring sensitizers.Herein this assumption is,how- and more on precisely engineering the material structure on ever,shown to be invalid for nanostructures.Wedemonstrate nanometer scale,inwhich energy migration behavior plays that excitation energy migration greatly affects upconversion akey role.Sofar, most of the related investigations have emission dynamics.“Dopant ions spatial separation” nano- focused on steady-state effects of energy migration.[5] That is, structures are designed as model systems and the intimate link excited states could randomly “walk”, thus making the long- between the random nature of energy migration and upcon- range energy transport (more than several nanometers) version emission time behavior is unraveled by theoretical between Ln3+ ions possible.However, the lack of adetailed modelling and confirmed spectroscopically.Based on this new microscopic picture of UC mechanism in such structures, fundamental insight, we have successfully realized fine control especially the ambiguous recognition of the energy migration of upconversion emission time behavior (either rise or decay dynamics and its effect on the time behavior of UC emission, process) by tuning the energy migration paths in various remains amajor bottleneck for further development of these specifically designed nanostructures.This result is significant structures. for applications of this type of materials in super resolution Based on traditional understanding,energy migration spectroscopy, high-density data storage,anti-counterfeiting, among sensitizers is always neglected in UC dynamics and biological imaging. treatment. In that case,although UC emission involves complex interactions between multiple Ln3+ ions,its dynamics Lanthanide (Ln) ions doped upconversion (UC) materials are solely determined by the energy transfer processes within have attracted extensive attention owing to their potential one activator–sensitizer pair (Figure 1a).[6] Despite some applications in alarge variety of fields,for example,display,[1] discussion of this assumption,[7] there is no direct evidence of the effect of the sensitizer-to-sensitizer energy migration on UC dynamics. [*] Dr.J.Zuo,[+] Dr.L.P.Tu,[+] Dr.B.Xue, Dr.Y.L.Zhang, Dr.Y.L.Chang, Prof. X. M. Liu, Prof. X. G. Kong, Prof. H. Zhang This unsatisfactory situation is primarily due to the lack of State Key Laboratory of Luminescenceand Applications, Changchun appropriate material systems.Indeed, even in the traditional Institute of Optics, Fine Mechanics and Physics, Chinese Academy of sensitizer–activator co-doping materials,energy migration Sciences still plays an important role in their UC process.[7a] However, Changchun 130033 (China) its effect is difficult to evaluate as the energy migration E-mail:[email protected] process is indistinguishable from energy transfer between [+] Dr.J.Zuo, sensitizers and activators.Inour opinion, this dilemma can be Universityofthe Chinese Academy of Sciences solved by introducing asmart nanosystem termed “dopant Beijing 100049 (China) ions spatial separation” (DISS) nanostructure.[5k] By locating Dr.J.Zuo[+] Dr.D.P.Sun,[+] Dr.Y.N.Wu, Prof. W. J. Buma, Prof. E. J. Meijer,Prof. H. Zhang sensitizers and activators into different regions of asingle Van’t Hoff Institute for Molecular Sciences, University of Amsterdam nanoparticle,the three basic processes of UC (i.e.light Science Park 904, 1098 XH Amsterdam(The Netherlands) absorption, energy migration, and UC emission) can be well E-mail:[email protected] separated (Figure 1b). Therefore,the role of energy migra- [email protected] tion in UC dynamics could be quantitatively determined by Dr.Y.H.Cao 1) tuning the migration layer thickness or 2) varying the College of Computer Science and Technology,Jilin University dopant concentration of the ions as energy carriers in the 2699 Qianjin Street, Changchun,Jilin 130021 (China) migration layer. Secondly,traditional treatment of the UC + [ ]These authors contributed equally to this work. mechanism based on simultaneous rate equations is not able Supportinginformation and the ORCID identification number(s) for to describe properly the actual energy migration processes, the author(s) of this article can be found under: because it provides only an averaged macroscopic statistical https://doi.org/10.1002/anie.201711606. result. Therefore,weset up atime-correlated Monte Carlo 2018 The Authors. Published by Wiley-VCH Verlag GmbH & Co. simulation model to fill the gap (Figure S1–S7, Table S1–S3, KGaA. This is an open access article under the terms of the Creative Commons Attribution Non-Commercial License, which permits use, in the Supporting Information). Compared with previous [5e,7a,8] distribution and reproduction in any medium, provided the original approaches, our model is capable of monitoring UC work is properly cited, and is not used for commercial purposes. dynamics from the level of multiple ion-to-ion interactions,

3054 2018 The Authors. Published by Wiley-VCH Verlag GmbH &Co. KGaA, Weinheim Angew.Chem. Int. Ed. 2018, 57,3054 –3058 Angewandte Communications Chemie

delay should be mainly attributed to the additional Yb3+ Yb3+ energy migration time under the 800 nm ! excitation. Significance of this result is that:1)itisthe first acquisition in real time of energy migration contribution to UC emission, and 2) it confirms that the energy migration temporal effect is non-negligible. This result is consistent with the prediction of Monte

Carlo simulation. In NaYF4 :20%Ybsublattice, despite each step of Yb3+ Yb3+ energy migration Figure 1. Schematic diagram of a) the traditional UC mechanism which relies on ! the monomer (sensitizer) to monomer (activator) sequential energy transfer only takes about 1.7 ms(Figure S5), and even if the interactions, and b) the UC process in the DISS nanostructure, in which the migration distance is just afew nanometers,the time three basic processes:photon absorption, energy migration, and UC emission delay for UC will still be several hundred micro- are spatially separated. seconds because 1) the random walk nature of energy migration, and 2) the non-linear nature of UC emis- yielding amore comprehensive vision without restric- tion of the distribution of Ln3+ ions in the nanostructure. Combining the experimental and simulation results,wefind that despite each step of the energy migration (e.g.Yb3+ Yb3+)only costs arelatively ! short time (around microseconds), its randomly walking nature significantly prolongs the migration time up to several hundred microseconds.This result tells us that the conventional understanding of the UC mechanisms is incomplete and in some nanostructures it might be misleading by ignoring the actual energy-migration process.More importantly, by precisely tuning energy migration paths in aDISS nanostructure,either the rise or decay of UC Figure 2. a) Schematic diagram of the experimental setup for binary pulsed emission dynamic traces can be quantitatively tail- (800 nm and 980 nm) excitation. b) The YbEr@Yb@YbNd UC nanostructure used in the binary pulsed excitation experiment. c) Time-gap (difference between ored in awide range.Our study thus not only offers 800 and 980 nm pulses) dependent UC emission intensity of the YbEr@Y- anew distinct microscopic picture on how energy b@YbNd nanoparticles (integrated from 500 nm to 700 nm). migration affects UC and the temporal characteristics of UC emission, but is also an excellent starting point for the rational design of novel functional and efficient UC sion (Figure S11). To validate this assumption, two types of nanostructures. DISS nanostructure are designed to tune the rise and decay of We prepared aDISS nanostructure:YbEr@Yb@ YbNd UC dynamics,respectively.

(short for NaYF4 :20% Yb,2%Er@NaYF4 :20% Yb To quantitatively tune the rise of the time trace of UC

@NaYF4 :10%Nd, 20%Yb) to explore the temporal effect of emission, the DISS nanostructure characterized with spatially energy migration. Thepure hexagonal phase of the nano- separated absorption (sensitizer) and emission (activator) particles was confirmed by the X-ray powder diffraction regions is suggested. As an example,the 800 nm excited (Figure S8). Theuniformed sizes (or thickness) of the core YbEr@Yb@Nd core/shell/shell nanostructure (short for and each shell were verified to be approximately 25.0 nm, NaYF4 :20% Yb,2%Er@NaLuF4 :20%

2.8 nm, 3.0 nm, respectively (Figure S9). To perform spectro- Yb@NaYF4 :20%Nd) is employed. TheUCemission of this scopic studies,abinary pulse excitation setup was designed, in structure relies fully on the Yb3+ Yb3+ energy transfer to ! which the interval (Dt)between a800 nm and a980 nm transport the absorbed energy from the outer layer to the core nanosecond pulse is tunable from 200 msto1000 ms(Fig- area (Figure 3a). Thepure hexagonal phase and narrow size À ure 2a). Typically,980 nm laser excites Yb3+ ions all over the distribution of nanoparticle are confirmed by Fourier-trans- whole nanoparticle,whereas 800 nm only excites Nd3+ ions form diffraction pattern and TEM images (Figures 3b and located in the outer layer (Figure 2b). TheUCemission Figure S12). Besides,the core/shell/shell structure is directly comes from 1) 980 nm excitation, 2) 800 nm excitation, and confirmed by distinguishing the lighter lanthanide element 3) 980 nm and 800 nm co-excitation. Clearly,the first two (Y,brighter parts) and the heavier one (Lu, darker parts) in parts (1 and 2) are Dt independent, and part (3) depends on the TEM image (Figures 3b). Clearly,because of the non- Dt. Strikingly,the strongest UC emission occurs not at Dt = 0, negligible Yb3+ Yb3+ energy migration time (ca. 1.7 msper ! 3+ but at the point when the 980 nm pulse is approximately step) in the NaLuF4 :20% Yb middle layer, the required 200 msbehind the 800 nm pulse (Figure 2c). Furthermore, time of Er3+ receiving the migrated energy can be well since the time constant of Nd3+ Yb3+ energy transfer is very controlled by the layer thickness,appearing as atunable rise ! short (ca. 20 ms, Figure S10), the approximately 200 mstime of UC luminescence time trace.Indeed, increasing the

Angew.Chem. Int.Ed. 2018, 57,3054 –3058 2018 The Authors. Published by Wiley-VCH VerlagGmbH &Co. KGaA,Weinheim www.angewandte.org 3055 Angewandte Communications Chemie

ing extra energy transfer channels.[11a, 12] However,all these approaches usually bring along limitations including 1) alimited tuning range,and 2) UC efficiencyreduction. Herein, we propose anovel strategy,that is,utilizing the energy migration process in DISS nanostructures characterized with partly overlapped sensitizer and activator regions.Asan example,aseries of YbEr@Yb core/active shell DISS

nanostructures (short for NaYF4 :20% Yb,2%

Er@NaYF4 :20% Yb) were synthesized. Thehigh quality of the nanostructures is confirmed by SEM images in Supporting Information (Figure S16). As shown in Figure 4a,b,the UC processes in this DISS nanostructure can be roughly divided into three parts.Inpart I, Yb3+ and Er3+ are co-doped, therefore Figure 3. a) Schematic representation of the UC process in the YbEr@Yb@Nd its UC emission dynamics presents as arelatively DISS nanostructure under 800 nm excitation. b) Typical TEM image (left), sharp rise due to the minimal energy migration time expanded area of TEM image (upper right) and Fourier-transform diffraction (black curve in Figure 4b). On the contrary,for patterns (lower right) of the YbEr@Yb@Nd nanostructure. c) The energy migra- parts II and III, the spatially separated Yb3+ and Er3+ tion distance (i.e. middle layer thickness) dependent 540 nm UC emission traces. Solid traces are the experimental results and dotted traces are the require the excitation energy to migrate with more simulation results. d) The influence of Yb3+ dopant concentration in the middle time to achieve UC emission, which leads to 1) slower layer (ca. 2.5 nm) on the 540 nm UC emission traces. rises,and 2) relatively low UC efficiencydue to the energy loss in the migration process (the green line and blue line in Figure 4b). Notably,the UC emission thickness of middle layer from 0toabout 4.5 nm results in time trace is aprofile of contributions of all the three parts, 4 prolongation of rise of around 540 nm UC emission ( S3/2 thus it makes the decay longer than any of the individual parts energy state) from 195 to 390 ms(Figure 3c,solid traces). (Figure 4b). As indicated in Figure 4c,the UC emission (ca. 4 Similar result has also been observed for F9/2 energy state (ca. 540 nm) decay lifetime (the required time for transient 650 nm UC emission), which varies from 383 to 607 ms emission intensity to decay from its maximum value to its 1/ (Figure S13). evalue) could be tuned over awide range from 139 to 648 ms Note that without the long-distance energy migration, by varying the active shell thickness from 0to15nm. such alarge time span modulation of the rise is hardly Meanwhile,the rises change little (from 36 to 144 ms, Fig- achieved in traditional Yb3+/Er3+ co-doping systems.[7e,9] ure S17) because they are all dominated by the common Importantly,such atuning effect is well predicted by our part I. Thesignificance of the results is that 1) it breaks simulation model (Figure 3c,dotted traces). Theonly excep- through the limitation of the traditional co-doping system. tion is the sample without amiddle layer (the red solid and dotted traces in Figure 3c). Thedeviation most probably comes from the model simplification, which ignores the efficient Er3+ Nd3+ energy ! quenching process.[5f] In addition, the influence of Yb3+ dopant concertation on energy migration dynamics has been studied. As shown in Figure 3d, the migration time will decrease as the Yb3+ dopant concertation increases.The reason is discussed in details in Supporting Information (Figure S14 and Table S4). Furthermore,toverify the universality of our approach, another DISS nanostructure,that is,

NaYF4 :20% Yb,2%Er@NaYF4 :20% Yb

@NaYF4 :10% Nd, 20%Yb has been tested, and similar results were obtained (Figure S15). Next we turn to tune the decay of time-resolved UC emission in awide range,which is not only required for practical applications,[10] but also very Figure 4. a) Schematic representation of UC processes in YbEr@Yb core/active important for an in-depth understanding of the UC shell nanostructure under the 980 nm excitation. b) Schematic representation of mechanism.[11] Up to now,modulation approach was UC emissiontrace of YbEr@Yb nanostructure (red line) and its equivalent emission origins (black trace from part I, green trace from part II, and blue trace almost exclusively addressed by changing the depop- from part III). Shell thickness dependent 540 nm UC emission traces of the ulation rate of the activator emitting energy level, c) core/activeshell structures and d) core/inert shell structures. e) 540 nm 3+ such as surface modification, Ln dopant concen- decay lifetimes (left) and 540 nm UC emissionintensities (right) of core/inert tration manipulation, plasmonic effect and introduc- shell structures (black curve) and core/active shell structures (red curve).

3056 www.angewandte.org 2018 The Authors. Published by Wiley-VCH VerlagGmbH &Co. KGaA,Weinheim Angew.Chem. Int. Ed. 2018, 57,3054 –3058 Angewandte Communications Chemie

Without the assistance of energy migration in the shell, Conflict of interest YbEr@Y core/inert shell structures (short for NaYF4 :20%

Yb,2%Er@NaYF4), as acontrol, offer arelatively narrow Theauthors declare no conflict of interest. tuning range (from 139 to 330 ms) via eliminating the surface quenching effect (Figure 4d). 2) It guides us to reconsider the Keywords: core–shell nanostructures ·energy migration · relationship between UC efficiency and decay lifetime.Based lanthanides ·luminescence dynamics ·Monte Carlo simulation · on the empirical views developed from sensitizer-activator co- upconversion nanocrystals doping systems,the longer UC emission decay lifetime is often related to ahigher UC efficiency due to the reduction of Howtocite: Angew.Chem. Int. Ed. 2018, 57,3054–3058 nonradiative relaxation rate.This view is,however,not always Angew.Chem. 2018, 130,3108–3112 valid to DISS nanostructures.Asindicated in Figure 4e, compared with YbEr@Y nanostructure,the YbEr@Yb DISS [1] a) R. Deng, F. Qin, R. Chen, W. Huang,M.Hong,X.Liu, Nat. nanostructure exhibits arelatively long decay lifetime but Nanotechnol. 2015, 10,237 –242;b)C.Zhang,L.Yang,J.Zhao, arelatively low UC efficiencywhen the shell thickness is over B. Liu, M. Y. Han, Z. Zhang, Angew.Chem. Int. Ed. 2015, 54, 6nm. This “abnormal” phenomenon can be explained by 11531 –11535; Angew.Chem. 2015, 127,11693 –11697;c)L. Wang,Y.Li, Nano Lett. 2006, 6,1645 –1649. 1) the energy migration effect of the active shell (prolonging [2] a) Q. Su, W. Feng,D.Yang,F.Li, Acc. Chem. Res. 2017, 50,32– the decay lifetime) and 2) the efficient energy back-transfer 40;b)N.M.Idris,M.K.Gnanasammandhan, J. Zhang,P.C.Ho, from core to active shell (decreasing the UC efficiency) R. Mahendran, Y. Zhang, Nat. Med. 2012, 18,1580 –1585;c)D. (Figure S18,19 and Table S5). It is quite gratifying to notice Wang,B.Xue,X.Kong,L.Tu, X. Liu, Y. Zhang,Y.Chang,Y. that the “abnormal” phenomenon is well predicted by our Luo,H.Zhao,H.Zhang, Nanoscale 2015, 7,190 –197;d)C. Monte Carlo simulations (Figure S20 and Table S6). Drees,A.N.Raj, R. Kurre,K.B.Busch, M. Haase,J.Piehler, In summary,long-standing puzzle of the intimate link Angew.Chem. Int. Ed. 2016, 55,11668 –11672; Angew.Chem. 2016, 128,11840 –11845;e)X.Li, Z. Guo,T.Zhao,Y.Lu, L. between excitation energy migration and UC emission Zhou, D. Zhao,F.Zhang, Angew.Chem. Int. Ed. 2016, 55,2464 – dynamics is unraveled through theoretical modeling and 2469; Angew.Chem. 2016, 128,2510 –2515;f)Y.Yang,Q.Shao, spectroscopic experiments of specifically designed “dopant R. Deng,C.Wang,X.Teng,K.Cheng,Z.Cheng,L.Huang,Z. ions spatial separation” nanostructure.The contribution of Liu, X. Liu, B. Xing, Angew.Chem. Int. Ed. 2012, 51,3125 –3129; excitation migration to the UC emission dynamics is demon- Angew.Chem. 2012, 124,3179 –3183;g)L.Cheng,K.Yang,Y. strated to be significant as aresult of the accumulative effect Li, J. Chen, C. Wang,M.Shao,S.T.Lee,Z.Liu, Angew.Chem. Int. Ed. 2011, 50,7385 –7390; Angew.Chem. 2011, 123,7523 – of multiple-step random walks of the excitation energy.Based 7528;h)S.H.Nam, Y. M. Bae,Y.I.Park, J. H. Kim, H. M. Kim, on this improved understanding,wepropose and demonstrate J. S. Choi, K. T. Lee,T.Hyeon, Y. D. Suh, Angew.Chem. Int. Ed. aconvenient and effective approach for tailoring UC 2011, 50,6093 –6097; Angew.Chem. 2011, 123,6217 –6221;i)L. dynamics (either the rise or decay) through tuning the Xia, X. Kong,X.Liu, L. Tu,Y.Zhang,Y.Chang,K.Liu, D. Shen, excitation energy migration paths in “dopant ions spatial H. Zhao,H.Zhang, Biomaterials 2014, 35,4146 –4156;j)S.Li, L. separation” nanostructures.Our study paves the way for Xu, W. Ma, X. Wu,M.Sun, H. Kuang, L. Wang,N.A.Kotov,C. application-optimized design of novel functional UC nano- Xu, J. Am. Chem. Soc. 2016, 138,306 –312;k)X.Yang,H.Xie, E. Alonas,Y.Liu, X. Chen, P. J. Santangelo,Q.Ren, P. Xi, D. Jin, structures and even to improve the UC emission efficiency. Light:Sci. Appl. 2016, 5,e16134. [3] a) X. Liu, Y. Wang,X.Li, Z. Yi,R.Deng,L.Liang,X.Xie, D. T. B. Loong,S.Song,D.Fan, A. H. All, H. Zhang,L.Huang, Acknowledgements X. Liu, Nat. Commun. 2017,https://doi.org/10.1038/s41467-017- 00916-00917;b)Y.Zhang,L.Zhang,R.Deng,J.Tian, Y. Zong, This work was financially supported by NSF of China D. Jin, X. Liu, J. Am. Chem. Soc. 2014, 136,4893 –4896;c)H. (11374297, 61575194, 11674316, 11504371, 11471278 and Liu, M. K. G. Jayakumar, K. Huang,Z.Wang,X.Zheng,H. Agren, Y. Zhang, Nanoscale 2017, 9,1676 –1686;d)K.Huang, 11604331), Project of Science and Technology Agency, Jilin N. M. Idris,Y.Zhang, Small 2016, 12,836 –852;e)J.Zuo,Q.Li, Province (20170520113JH, 20170520112JH and B. Xue,C.Li, Y. Chang,Y.Zhang,X.Liu, L. Tu,H.Zhang,X. 20170519002JH), Joint research program between CASof Kong, Nanoscale 2017, 9,7941 –7946. China and KNAW of the Netherlands,European Union [4] a) M. He,X.Pang, X. Liu, B. Jiang,Y.He, H. Snaith, Z. Lin, MSCA-ITN-ETN Action program, ISPIC,under grant Nr. Angew.Chem. Int. Ed. 2016, 55,4280 –4284; Angew.Chem. 675743, Netherlands Organisation for Scientific Research in 2016, 128,4352 –4356;b)X.Huang,S.Han, W. Huang,X.Liu, Chem. Soc.Rev. 2013, 42,173 –201;c)W.Zou, C. Visser,J.A. the framework of the Fund New Chemical Innovation under Maduro,M.S.Pshenichnikov,J.C.Hummelen, Nat. Photonics grant Nr.731.015.206, European COST Action (CM1403), 2012, 6,560 –564. John van Geuns Fellowship under auspices of the HRSMC [5] a) X. Li, X. Liu, D. M. Chevrier,X.Qin, X. Xie,S.Song,H. and Innovation project of State Key Laboratory of Lumines- Zhang,P.Zhang,X.Liu, Angew.Chem. Int. Ed. 2015, 54,13312 – cence and Applications of China. Thework of Dr. D. P. Sun is 13317; Angew.Chem. 2015, 127,13510 –13515;b)X.Chen, L. supported by the research program of the “Stichting voor Jin, T. Sun, W. Kong,S.F.Yu, F. Wang, Small 2017,https://doi. Fundamenteel Onderzoek der Materie (FOM)”, which is org/10.1002/smll.201701479;c)N.J.J.Johnson, S. He,S.Diao, E. M. Chan, H. Dai, A. Almutairi, J. Am. Chem. Soc. 2017, 139, financially supported by the Nederlandse Organisatie voor 3275 –3282;d)X.Chen, L. Jin, W. Kong,T.Sun, W. Zhang,X. Wetenschappelijk Onderzoek (NWO). Liu, J. Fan, S. F. Yu,F.Wang, Nat. Commun. 2016, 7,10304;e)Y. Zhong,I.Rostami, Z. Wang,H.Dai, Z. Hu, Adv.Mater. 2015, 27, 6418 –6422;f)Y.Zhong,G.Tian, Z. Gu, Y. Yang,L.Gu, Y.

Angew.Chem. Int.Ed. 2018, 57,3054 –3058 2018 The Authors. Published by Wiley-VCH VerlagGmbH &Co. KGaA,Weinheim www.angewandte.org 3057 Angewandte Communications Chemie

Zhao,Y.Ma, J. Yao, Adv.Mater. 2014, 26,2831 –2837;g)J. 7605 –7609; Angew.Chem. 2017, 129,7713 –7717;b)D.J. Wang,R.Deng,M.A.MacDonald, B. Chen, J. Yuan, F. Wang,D. Gargas,E.M.Chan, A. D. Ostrowski, S. Aloni, M. V. P. Altoe, Chi, T. S. A. Hor, P. Zhang,G.Liu, Y. Han, X. Liu, Nat. Mater. E. S. Barnard, B. Sanii, J. J. Urban, D. J. Milliron, B. E. Cohen, 2014, 13,157 –162;h)F.Wang,R.Deng,J.Wang,Q.Wang,Y. P. J. Schuck, Nat. Nanotechnol. 2014, 9,300 –305;c)R.Deng, J. Han, H. Zhu, X. Chen, X. Liu, Nat. Mater. 2011, 10,968 –973; Wang,R.Chen, W. Huang,X.Liu, J. Am. Chem. Soc. 2016, 138, i) Q. Su, S. Han, X. Xie,H.Zhu, H. Chen, C. K. Chen, R.-S.Liu, 15972 –15979;d)D.Khoptyar, S. Sergeyev,B.Jaskorzynska, J. X. Chen, F. Wang,X.Liu, J. Am. Chem. Soc. 2012, 134,20849 – Opt. Soc.Am. B 2005, 22,582 –590;e)E.M.Chan, G. Han, J. D. 20857;j)M.Ding,D.Chen, D. Ma, J. Dai, Y. Li, Z. Ji, J. Mater. Goldberg,D.J.Gargas,A.D.Ostrowski, P. J. Schuck, B. E. Chem. C 2016, 4,2432 –2437;k)L.Tu, X. Liu, F. Wu,H.Zhang, Cohen, D. J. Milliron, Nano Lett. 2012, 12,3839 –3845. Chem. Soc.Rev. 2015, 44,1331 –1345. [9] J. Zhao,Z.Lu,Y.Yin, C. McRae,J.A.Piper,J.M.Dawes,D.Jin, [6] a) F. Auzel, Chem. Rev. 2004, 104,139 –173;b)M.J.Weber, E. M. Goldys, Nanoscale 2013, 5,944 –952. Phys.Rev.B1971, 4,2932 –2939;c)W.J.C.Grant, Phys.Rev.B [10] Y. Lu, J. Zhao,R.Zhang,Y.Liu, D. Liu, E. M. Goldys,X.Yang, 1971, 4,648 –663. P. Xi, A. Sunna, J. Lu, Y. Shi, R. C. Leif,Y.Huo,J.Shen, J. A. [7] a) M. Y. Hossan, A. Hor, Q. Luu, S. J. Smith, P. S. May,M.T. Piper,J.P.Robinson, D. Jin, Nat. Photonics 2014, 8,33–37. Berry, J. Phys.Chem. C 2017, 121,16592 –16606;b)S.Alyatkin, [11] a) W. Zheng,P.Huang,D.Tu, E. Ma, H. Zhu, X. Chen, Chem. I. Asharchuk, K. Khaydukov,A.Nechaev, O. Lebedev,Y. Soc.Rev. 2015, 44,1379 –1415;b)R.B. Anderson,S.J.Smith, Vainer,V.Semchishen, E. Khaydukov, Nanotechnology 2017, 28, P. S. May,M.T.Berry, J. Phys.Chem. Lett. 2014, 5,36–42. 035401;c)D.A.Zubenko,M.A.Noginov,V.A.Smirnov,I.A. [12] G. Chen, H. Qju, P. N. Prasad, X. Chen, Chem. Rev. 2014, 114, Shcherbakov, Phys.Rev.B1997, 55,8881 –8886;d)P.Villa- 5161 –5214. nueva-Delgado,K.W.Kraemer,R.Valiente, J. Phys.Chem. C 2015, 119,23648 –23657;e)S.Fischer,N.D.Bronstein, J. K. Swabeck, E. M. Chan, A. P. Alivisatos, Nano Lett. 2016, 16, 7241 –7247. Manuscript received:November13, 2017 [8] a) Q. Chen, X. Xie,B.Huang,L.Liang,S.Han, Z. Yi,Y.Wang, Acceptedmanuscript online: January 24, 2018 Y. Li, D. Fan, L. Huang,X.Liu, Angew.Chem. Int. Ed. 2017, 56, Version of record online: February 14, 2018

3058 www.angewandte.org 2018 The Authors. Published by Wiley-VCH VerlagGmbH &Co. KGaA,Weinheim Angew.Chem. Int. Ed. 2018, 57,3054 –3058